catena-Poly[[bis(nitrato-κ2 O,O′)zinc(II)]-μ-4,4′-bis(pyrazol-1-ylmethyl)biphenyl-κ2 N 2:N 2′]

In the title compound, [Zn(NO3)2(C20H18N4)]n, the ZnII atom lies on a crystallographic twofold axis and the coordination geometry can be considered as a slightly distorted tetrahedron defined by two O atoms from two nitrate groups and two N atoms from two ligand molecules. A distorted octahedron may be assumed when two of the symmetry-related nitrate O atoms, with Zn—O distances of 2.528 (2) Å, are added to the coordination environment. Another twofold axis, passing through the middle of the biphenyl bonds, is observed in the crystal structure. A chain along [101] is built up by the ligands linking the ZnII ions.

In the title compound, [Zn(NO 3 ) 2 (C 20 H 18 N 4 )] n , the Zn II atom lies on a crystallographic twofold axis and the coordination geometry can be considered as a slightly distorted tetrahedron defined by two O atoms from two nitrate groups and two N atoms from two ligand molecules. A distorted octahedron may be assumed when two of the symmetry-related nitrate O atoms, with Zn-O distances of 2.528 (2) Å , are added to the coordination environment. Another twofold axis, passing through the middle of the biphenyl bonds, is observed in the crystal structure. A chain along [101] is built up by the ligands linking the Zn II ions.

Related literature
For a related polymeric bis(pyrazole) dinitratocobalt(II) structure, see: Chen et al. (1997). For the synthesis and structure of a three-dimensional polymeric Zn(II) network compound, see: Zhu et al. (2002).

Comment
The structures of the metal derivative 1,4-bis(pyrazole) benzene are known for zinc and cobalt (Chen et al., 1997). In order to enrich the research of this kinds of ligand, a new ligand 4,4'-bis(pyrazole) biphenyl with longer spacer was synthesized, and which are used in the preparation of coordination compound with zinc dinitrate.
The central Zn atom lies on a crystallographic twofold axis and the coordination geometry can be considered as a slightly distorted tetrahedron defined by two O atoms from two nitrate groups and two N atoms from two ligand molecules. A distorted octahedron may be assumed when two of the C 2 related nitrate oxygen atoms with Zn-O distances of 2.528 (2) Å are added (Table 1)

Refinement
H atoms bound to C atoms were placed in calculated positions and treated as riding on their parent atoms, with C-H = 0.93 Å (aromatic), C-H = 0.97 Å (methylene), and with U iso (H) = 1.2U eq (C). Fig. 1. The molecular structure of the title compound, showing the atom-labeling scheme and displacement ellipsoids drawn at the 50% probability level. symmetry codes: i = -x + 1, y, -z -0.5; ii = -x + 2, y, -z + 0.5 Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.